Gram-Positive Bacteria

Gram Stain

Technique to classify bacteria by cell wall properties.

Pathogenic Features

Characteristics that enable bacteria to cause disease.

Staphylococcus spp.

Genus of bacteria

Coagulase

Enzyme that causes blood clotting

S. aureus

Highly virulent Staphylococcus species

Coagulase-Negative Staphylococcus

Less pathogenic Staphylococcus

Facultative Anaerobes

Bacteria that can grow with or without oxygen.

Hyaluronidase

Enzyme that breaks down hyaluronic acid in tissues.

Leucocidin

Toxin that damages white blood cells.

Hemolysin

Toxin that lyses red blood cells.

Enterotoxin

Toxin causing food poisoning and gastrointestinal symptoms.

Methicillin Resistant Staphylococcus aureus (MRSA)

Strain of S. aureus resistant to methicillin antibiotics.

Morphology

Study of bacterial shape and arrangement.

CBC with Differential

Blood test to assess different types of blood cells.

Cultures

Laboratory method to grow and identify bacteria.

Specimens

Samples collected for laboratory testing

Gram Positive

Bacteria that retain crystal violet stain during gram staining.

Sputum

Mucus from the respiratory tract

Cerebral Spinal Fluid

Fluid surrounding the brain and spinal cord

Fibrinolysin

Enzyme that breaks down fibrin in blood clots.

Capsule

Protective layer surrounding some bacteria

Toxic Shock Syndrome

Severe condition caused by toxins

Staphylococcus aureus

Normal flora; causes nosocomial and community infections.

MSSA

Methicillin-susceptible Staphylococcus aureus.

MRSA

Methicillin-resistant Staphylococcus aureus; resistant to β-lactams.

PBP2a

Protein that confers methicillin resistance in MRSA.

Coagulase-negative Staphylococci

Low virulence; common skin flora with >45 species.

S. epidermidis

Common CoNS; often a contaminant in blood cultures.

S. saprophyticus

CoNS; associated with urinary tract infections.

S. pneumoniae

Common cause of community-acquired pneumonia.

S. pyogenes

Group A, Beta-hemolytic streptococcus causing skin and throat infections.

S. agalactiae

Group B, Beta-hemolytic streptococcus; associated with neonatal infections.

Viridans group streptococci

Group of bacteria causing infective endocarditis.

E. faecalis

Common enterococcus species, less resistant to antibiotics; weak pathogen; nosocomial infections

E. faecium

More prominent Enterococcus species; antibiotic resistant; linked to VRE

S. mutans

Streptococcus species primarily responsible for dental caries.

α-hemolytic

Streptococcus that partially lyses red blood cells.

β-hemolytic

Streptococcus that completely lyses red blood cells.

Pneumococcal vaccines

Prevent infections caused by S. pneumoniae.

Nafcillin

Anti-staphylococcal penicillin for MSSA treatment.

Vancomycin

Drug of choice for MRSA infections.

Ceftaroline

β-lactam antibiotic effective against MRSA.

MIC creep

Gradual increase in minimum inhibitory concentration.

Osteomyelitis

Bone infection often caused by Staphylococcus.

Bacteremia

Presence of bacteria in the bloodstream.

Sepsis

Severe systemic response to infection.

Beta-lactams

Antibiotics effective against various bacterial infections.

Fluoroquinolones

Broad-spectrum antibiotics, excluding Ciprofloxacin

Vancomycin

Antibiotic used for serious Gram-positive infections.

Linezolid

Oxazolidinone antibiotic for resistant infections.

Clindamycin

Antibiotic with variable activity against certain bacteria.

Tetracyclines

Broad-spectrum antibiotics with variable effectiveness.

Macrolides

Antibiotics with increasing resistance issues.

TMP/SMX (Bactrim)

Combination antibiotic with poor efficacy against some infections.

Impetigo

Skin infection common in children, caused by S. pyogenes

Rheumatic fever

Complication of untreated streptococcal throat infections.

Endocarditis

Infection of heart valves, associated with viridians group

Infective endocarditis

Infection of heart valves, often by enterococci

Opportunistic infections

Infections occurring in immunocompromised individuals.

Combination therapy

Using multiple drugs to enhance treatment effectiveness.

γ hemolytic

Type of hemolysis indicating no red blood cell lysis.

Beta-lactams

Class of antibiotics including penicillin derivatives.

Ampicillin

A broad-spectrum beta-lactam antibiotic.

Vancomycin

Glycopeptide antibiotic effective against Gram-positive bacteria.

Linezolid

Oxazolidinone antibiotic for resistant Gram-positive infections.

Daptomycin

Lipopeptide antibiotic for skin and soft tissue infections.

Lipoglycopeptides

Newer class including Oritavancin, effective against Gram-positives

Tigecycline

Glycylcycline antibiotic effective against VRE.

Clostridium tetani

Anaerobic bacterium causing tetanus via tetanospasmin toxin.

Tetanospasmin toxin

Blocks neurotransmitter, causing prolonged muscle transaction

Clostridium perfringens

Anaerobic bacterium causing gas gangrene and food poisoning.

α toxin

Exotoxin causing hemolysis and necrotizing soft tissue.

Clostridium botulinum

Produces botulinum toxin, causing respiratory paralysis

Botulinum toxin

Most potent toxin, inhibits acetylcholine release

Clostridium difficile

Anaerobic bacterium causing pseudomembranous colitis.

Pseudomembranous colitis

Inflammation of colon due to C. difficile toxins.

Toxin A

Enterotoxin causing diarrhea by binding GI tract.

Toxin B

Cytotoxin leading to cell death in GI tract.

Fecal transplant

Treatment to restore normal GI flora.

Corynebacteria diphtheriae

Causes diphtheria, produces exotoxin affecting the airway

Diphtheria

Infection characterized by membrane blocking the airway.

Gram-positive bacteria

Bacteria with thick peptidoglycan cell wall.